The present invention relates to interbody stabilization procedures of vertebrae in the spine, including fusions and disc space height restorations. A number of medical conditions such as compression of spinal cord nerve roots, degenerative disc disease, herniated nucleus pulposis, spinal stenosis and spondylolisthesis can cause severe low back pain. Restoration of the space between adjacent vertebrae and/or removal of the anatomical structure pushing against the spinal cord or exiting nerve roots is known to alleviate patient suffering. It is often desirable to stabilize the restored disc space by placing a spacer within the intervertebral space. Some intervertebral implants rest on the existing endplates while others either partially or completely extend into the adjacent intervertebral bodies. Access to the affected disc space is achieved from a variety of approaches to the spine which are the result of surgeon preference, patient anatomy, level of the spine affected and interbody implant selection.
A number of implant materials have been utilized to form interbody spacers. Many of these spacers are manufactured from metal or other very durable materials suitable for human implantation. Additionally, spacers are fashioned from bone, polymers, coral and other material suitable for implantation in the spine but having a greater tendency to fracture under high stresses.
In certain procedures, the loads applied to the implant during the insertion procedure exceed the loads that the implant may experience after implantation in the patient. The interface between the implant and the implant insertion tool may concentrate forces on weak areas of the implant during insertion. This area of concern is increased when implants are formed of materials having a tendency to crumble, crack or break as a result of experiencing high forces during insertion. For example, interbody fusion implants inserted from a transforaminal approach to the lumbar spine (TLIF approach) are typically forced to make a turn in the disc space to achieve the desired alignment. U.S. patent application Ser. No. 10/721,642 filed Nov. 25, 2003 by Frey et al. discloses instruments and techniques for unilateral implant positioning from a posterior approach to the spine and is incorporated herein by reference in it's entirety. It will be appreciated that in one aspect, the unilateral insertion technique uses the insertion tool to apply non-longitudinal forces to the implant to urge it across the disc space. Such forces may damage existing implants or inhibit the use of certain desirable materials for such implant designs.
Therefore, there remains a need for improved implant designs, configurations of the tool engagement surface on the implant, as well as improvement for the insertion tools utilized to grasp the implant during the insertion procedure.